Elevator control system



Oct. 24, 1933.

K. M. WHITE r AL ELEVATOR CONTROL SYSTEM Filed Jan. 6, 1931 4 Sheets-Sheet 1 III:

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ELEVATOR CONTROL SYSTEM Filed Jan. 6, 1931 4 Sheets-Sheet 2 l x I l I ,1 l I l l l/ v i WITNESSES: K g

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ATTORNEY Oct, 24,1933.- K. M. WHITE ET! AL ELEVATOR CONTROL SYSTEM Filed Jan. 6, 1931 4 Sheets-Sheet 3 INVENTORS Kermef/r/l W/z/fe A ATl ORNEY Oct. 24, 1933; K, WHITE ET A 1,931,564

ELEVATOR CONTROL SYSTEM Filed Jan. 6, 1931 I 4 Sheets-Shet 4 as fay;

INVENTORS. [HP/weft IY W/fl fe &

Patented Oct. 24, 1933 UNITED STATES ELEVATOR CONTROL SYSTEM Kenneth M. White, Chicago, 111., and Luther J.

Kinnard, Los Angeles, Calit., assignors to Westinghouse Electric Elevator Company, a

corporation of Illinois Application January 6, 1931. Serial No. 508,928

13 Claims.

Our invention relates to elevator-control syttems and has particular relation to elevatorcontrol systems in which the accuracy of landing depends, in part, at least, upon control of the mechanical brake. Although not limited thereto, our invention is particularly applicable to elevator systems of the geared-drive type.

In another aspect, our invention relates to relays of novel construction for use in control systemsgenerally, but of particular utility in elevator-control systems.

In elevator-control systems of the geareddrive-type, the motive power is furnished by a small, high-speed elevator motor connected to the hoisting drum through suitable reduction gearing. Where alternating-current power is used, the elevator motor is commonly a singlespeed or two-speed induction motor, started by means 01' primary resistance-control apparatus, or other suitable control apparatus. Motive equipment of this type has the advantage of great simplicity and ruggedness but. because of the constant-speed characteristic of the motor, does not permit of as high a degree of refinemer t in deceleration control as would, for all cases, bedcsirable.

With an induction-motor drive, regenerative braking cannot be used at speeds below the synchronous speed of the motor, lithe latter is of the single-speedtype, or below the synchronous speed of the low-speed winding, it the motor isof the two speed type, unless auxiliary apparatus for modifying the operation of the motor is provided. This auxiliary apparatus may assume a variety oi forms, depending upon the method by which the motor is to be braked. For example, if the motor is to be braked by reducing the supply frequency, auxiliary dynamo-electric apparatus is required for supplying the reduced frequency. If the motor is to braked by plugging, some form of speed-responsive device must be provided for interrupting the plugging connections when the motor is brought to rest. Because of these complications, which would be necessary for regeneratively braking the motor, it is, in many instances, preferable to rely entirely on the mechanical brake for stopping. For relatively low car speeds, ample braking effect may be obtained by means of the mechanical brake alone, without any sacrifice of the simplicity of the system.

If the mechanical brake alone is used for stopping, the motor is disconnected and the brake applied when the. elevator car is a predetermined distance in advance of the landing at which the car is to stop. The car then drifts, against the retarding force of the brake, to a position approximately level with the landing. Because of inequalities in the unbalanced load on .the. car, the car does not stop level with the 0 landing under all load conditions but tends to over-run with overhauling'loads and to underrun with driving loads."

During the stopping operation mentioned above, the brake must absorb an amount of mechanical 05 energy represented by a kinetic component, stored in the motor armature and other moving parts, plus or minus a potential component, representing the energy necessary to transfer the unbalanced load through the slow down distance. The 7 kinetic energy of the moving parts always acts in opposition to the braking-torque, whereas the potential energy representing the unbalanced load, assists the braking torque with driving loads and acts in opposition thereto with overhauling loads. It is apparent that both of these quantities are variable, the kinetic energy being a function of the car speed and the potential energy being a function of the unbalanced load. However, the' characteristics of an induction motor 39 (and also of a shunt motor) are such that, with constant supply voltage and constant resistance in the motor circuits, the motor speed falls with motoring loads and rises with overhauling or regenerative loads; there being a particular value of motor speed corresponding to each value of unbalanced load. The motor speed and the kinetic energy stored in the motor armature and .the parts driven thereby are, therefore, functions of the unbalanced load. As both the kinetic and potential components, which together determine the energy to be absorbed by the brake during slow down, are functions of the unbalanced load, it isapparent that, by a single correction of the braking torque in accordance with the unbalanced load, the car may be brought to rest in a substantially uniform slow-down distance, under all load conditions.

The power supplied to, or returned by, the elevator motor during operation at steady speed is an accurate index of the unbalanced load. However, at the time the braking effect is to be controlled, the elevator motor is disconnected. In order to control the mechanical brake in accordance with the unbalanced load, as measured by 5 the power flowing in the motor circuit, therefore, it is necessary to record the power flowing in the motor circuit while the motor is operating at steady speed and, afterwards, when themotor is disconnected, to control the braking effect in acno cordance with the recorded value. This, in accordance with our invention, is accomplished by means of a relay of novel construction, as will hereinafter more fully appear.

It is, accordingly, an object of our invention to provide a relay of novel construction, which may be connected to respond to the power or current flowing in an external circuit, having an armature which, upon interruption of the external circuit, will remain in the position in which it was at the instant before the interruption.

Another object of our invention is to provide an elevator system in which the time element of the brake discharge circuit shall be adjusted in accordance with the power flowing, in the motor circuit at the instant before the motor circuit is interrupted, so that the elevator car may be brought to rest by the action of the mechanical brake, in approximately the same distance of car travel under all load conditions.

Another object of our invention is to provide a push-button-controlled elevator system in which the car shallbe automatically stopped at the first landing in advance of the car at which a hall button is pushed when the car is lightly loaded, but in which the car cannot be stopped in response to the hall buttons when the car load exceeds a predetermined value.

Other objects of our invention will become evident from the following detailed description, taken in conjunction with the accompanying drawings, in which:

Figure 1 is a view, in front elevation, of a relay embodying our invention, parts being broken away and in section for clearness.

Fig. 2 is a plan view of the relay shown in Fig. 1, the cover plate being removed.

Fig. 3 is a sectional view, taken on the line III-III of Fig. 1, parts being broken away for clearness.

Fig. 4 is a view, in side elevation, of the relay shown in Fig. 1, the cover plate being partially broken away.

Fig. 5 is a fragmentary sectional view of a detail of the relay shown in Fig. 1, taken on the line VV of Fig. 2.

Fig. 6 is a diagrammatic view of a relay constructed in accordance with the present invention and connected to respond to power flow.

Fig. 7 is a diagrammatic view of an elevator system organized in accordance with the present invention.

Fig. 8 is a diagrammatic view showing the relative positions of hatchway switches and the elevator car in the system shown in Fig. 7.

Referring to the drawings, the apparatus shown in Figs. 1 to 5 comprises a base plate 1 (see Fig. 3), of suitable insulating material, upon which are secured a pair of brackets 2 and 3, by means of any suitable fastening members 4 and 5. A pair of U-shape magnetic members 6 and 7 are supported by the brackets 2 and 3, in such relative positions that the sides of the U-shape members are in alignment and separated by an air gap. The members 6 and 7 are fastened to the brackets 2 and 3 by bolts or other suitable fastening members 8. A current coil 9 and a voltage coil 10 are mounted on the outer legs of the magnetic members 6 and 7, respectively, and are held in place by non-magnetic bracing members do and 7a, riveted or otherwise suitably secured across the open ends of the magnetic members.

As best shown in Fig. 4, a bracket 11 is secured to the base plate 1 by means of rivets or other suitable fastening members 11a, in a position between the brackets 2 and 3. The free end of the bracket 11 is drilled and internally threaded tov receive an externally threaded bearing cup 12 (SeeFig. 1). An armature 13 is pivotally mounted upon a ball 12a held in the bearing cup 12, in such position that it lies in the air gap between the ends of the magnetic members 6 and 7. The armature 13 comprises a frame portion 14, an armature coil 15 and a contact arm 16, best shown in Fig. 3. Returning to Fig. 1, frame portion 14 consists of strips of non-magnetic material riveted together to form a square coil-supporting member 14a and a.contact-arm-supporting member 14b. The armature coil 15 is mounted on a copper tube 15a secured to the coil supporting member 14a. As best shown in Fig. 3, the con tact arm 16 comprises a tube 16a in which two small contact brushes 17 and 18 are resiliently mounted. The contact brushes 17 and 18 comprise pin portions which extend through holes in the supporting member 14b and shoulder portions which are biased against the supporting member by a spring 16b.

In addition to supporting the magnetic members 6 and 7, the brackets 2 and 3 also serve as supports for a contact panel 19, (see Fig. 1) preferably of molded insulating material, upon which are mounted terminal posts 20 and a pair of resistors T1 and r2. As shown in Fig. 5, a bearing pin 22 and a plurality of contact segments 23 of L-shaped are embedded in the plate 19 in such relative positions that the segments 23 extend radially about the bearing pin.

The part of the contact plate 19 adjacent to the segments 23 is shaped to constitute a cylindrical projection 1941, having a central opening 192;, into which the ends of the segments 23 extend. Arcuate slots 19c extend downward from the upper surface of the contact plate 19 and intersect the opening 19b. The construction produced by the opening 19b and slots 19c is such that the bearing pin 22 is supported in the center of the opening 19?: by means of a bridging member 19d integral with the contact plate 19. The inner ends of the contact segments 23 are disposed in a circular path in position to be engaged by the contact pins 17 and 18. It will be noted thatthe segments 23 are divided into two groups on opposite sides of the contact arm, the groups being staggered with respect to a line passing through the axis of rotor 13. Because of this construction, the contact arm 16, upon rotation, alternately engages the contact segments of each group, to thereby provide a maximum number of contact points for a given angular displacement of the armature 13.

The contact segments 23 are connected, by suitable conductors, (not shown) to taps of the resistors 11 and r2.

A cover plate 26, having a glass window 27 mounted therein, is secured to the base plate 1 by means of suitable bolts 28, best shown in Fig. 3.

The operation of the relay described above may best be understood by reference to Fig. 6 which shows, diagrammatically, a circuit embodying the relay. Referring to Fig. 6, the apparatus shown therein comprises a relay A of the type illustrated in Figs. 1 to 5, diagrammatically shown in connection with a circuit including a non-inductive load device R and an inductive load device L. g

The relay A comprises a pivotally mounted armature 13, upon which is mounted an armature coil 15 and a contact arm 16. The current coil 9 and the voltage coil 10 of therelay are of the relay A are connected, in parallel, to the conductors B and C. The current coil 9 of the relay is connected, in series with the conductor C, between the ,switch S1 and the load devices R and L.

The magnetic members 6 and 7 constitute ma netic paths of relatively high reluctance, because of their small cross section and relatively long air gaps. The magneticmembers, do not, therefore, greatly increase the inductance of the coils 9 and 10. The coils 9, 10 and 15 are each designed to haverelatively small reactance, at power frequencies, in comparison with their resistance.

The operation of the apparatus shown in Fig. 6 may be set forth as follows: upon closure of the switch S1, the potential coil 10 and the arma-,

ture coil 15 are connected to the source S. As the inductive reactance oi the coils l0 and 15 is small in comparison with their resistance, these coils now generate alternating magnetomotive forces which are substantially in phase with each other. The magnetomotive force generated by the potential coil 10 produces an alternating flux, part of which follows the magnetic circuit comprising the magnetic member '7 and the air gap between its ends, and the remainder of which follows leakage paths through the air surrounding the coil 10. J

Because. of the length of the air gap between the ends of the member 7, the leakage flux is considerable, and, in consequence, the leg of the magnetic member upon which the coil is disposed is a stronger magnetic pole than the other end. Because of the current flowing in the armature coil 15, the armature turns to such position that the coil 15 interlinks the maximum number of lines of flux emanating iromthe' ends of the member '7. This position is approximately that ,in which the axis of the armature coil 15 is parallel to the upper leg of the magnetic member 7.

The position in which the armature now lies is the position corresponding to zero power in the external circuit BC. We have illustrated contact members 23a to 23c so positioned with respect to the contact arm 16 that, when the relay armature is in the position corresponding to zero power, the contact arm 16 engages the end contact member 23a. With this arrangement, the relay responds only to power flowing in one direction in the circuit B-C. It will be understood, however, that we may so position the contact members 23a to 23s that, when the 'relay armature is in the position corresponding to zero power, the contact arm will engage an intermediate contact member, such as 230. With the latter arrangement, the relay is responsive to power flowing in either direction in the external circuit.

Returning to Fig. 6, if the switch S2 is closed, a current in phase with the line voltage is drawn by the non inductive load device R. This current, in flowing through the coil 9, generates a magnetomotive force in phase with the magnetomotive forces produced by the potential coil 10 and the armature coil 15. The magnetomotive force generated by coil 9 produces a flux, part of which follows the magnetic circuit comprising the magnetic member 6 and the air gap between its ends, and part of which follows leakage paths through the air surrounding the coil 9. The direction of the flux produced by coil 9 is such that the upper end of the magnetic member 6 is of the opposite polarity to the upper end of the magnetic member 7.

The flux produced by coil 9 distorts the mag- .netic field in which the armature coil 15 is situated and causes the armature 13 to turn, counter-clockwise, to such position that the armature coil 15 again interlinks the maximum number of lines of flux of the field in which it is situated." As the amount of field distortion produced by the current coil 9 depends upon the current flowing in conductor C, there is a definite stable angular position of the armature 13 for each value of current flowing in the conductor C.

If the switch S2 is opened, the armature 13, because of the reaction of coils 10 and 15 upon each other, rotates clockwise to the position of zero power, in which the contact arm 16 engages the contact member 23a.

If the switch S3 is now closed, the inductive device L is connected to the source S and draws a lagging current, which, for purposes of illus-- tration, we shall assume to be out of phase with the voltage of source S. The lagging current, flowing in the coil 9, produces a flux which is 90 out of phase with the flux produced by the coils 10 and 15. The flux produced by the coil 15 is, therefore, zero when the flux produced by the coil 9 is a maximum, and the flux produced by the coil 15 is a maximum when the flux produced by the coil 9 is zero.

During a half cycle of the flux produced by coil 9, the iiux produced by the coil 15 passes from a maximum in one direction, through zero, to a maximum in the other direction, tending to rotate the armature in one direction during the first quarter cycle and to rotate it in the opposite direction during the second quarter cycle. During the next half cycle, the process described above is repeated, continuing indefinitely. The angular impulses given to the armature 13 because of the lagging current in the coil 9.are equal I and opposite during succeeding quarter cycles, so that an alternating torque of doublethe line frequency is impressed on the armature 13. As the armature has sufficient inertia to prevent its response to this rapidly alternating torque, the

armature is unaffected and remains in the position corresponding to zero power.

If, while the switch S3 remains closed, the switch S2 is reclosed, a current having a power component corresponding to the current drawn by the non-inductive load R and a reactive component corresponding to the current drawn by the inductive load L, flows in the circuit B--C. This current, in flowing through the coil 9, produces a flux which lags the flux produced by coils 9 and 10 by some angle less than 90. The lagging flux produced by the coil 9 may be resolved into a component in phase with the flux produced by coils 10 and 15 and a component 90 out of phase with that flux. The component which is in phase with the flux produced by the coils 10 and 15 is proportional to the current drawn by the non-inductive load R and causes the armature 15 to turn, counterclockwise, to a position corresponding to the current drawn by the load device R. The component which is 90out of phase with the flux produced by the coils 10 and 15 sets up. a

double-frequency torque upon the armature 13, as previously explained, but does not aflect the position of the armature.

It will be readily seen from the above that the relay A responds only to the power component of current flowing in the circuit with which it is connected and does not respond to the reactive component. Assuming that the line voltage remains constant, the position of the armature of the relay A is a measure of the power flowing in the external circuit.

It will be noted that, in the arrangement described above, the voltage coil 10 acts as a means for biasing the armature 13 to a position corresponding to zero power, and that the current coil 9 tends to turn the armature against its bias. If, while the switches S2 and S3 are closed, the switch S1 is opened, the circuits of coils 9, l0 and 15 are broken simultaneously. The interruption of the circuit of coil 9 removes the force tending to-turn the armature against its bias. However, the interruption of the circuits of coils 10 and 15 removes the bias, so that all forces acting on the armature are simultaneously removed. The relay armature does. not, therefore, return to the position corresponding to zero power, but remains in the position in which it was at the instant before the power circuit was interrupted.

Whereas, in order to illustrate the eflect of reactive current upon the relay described above, we have described it in connection with an alternating-current circuit, it will be appreciated that the reactions of coils 9, 10 and 15 upon each other are such that the relay may, with equal facility, be used in direct current circuits, as a power or current-responsive device.

Figs. 7 and 8 show, diagrammatically, an application of our invention to a push-button-controlled elevator system of the collector type, with single-speed induction-motor drive.

Referring to Fig. 7, the apparatus shown comprises a single-speed, induction elevator-motor 30 mechanically connected, through suitable gearing 31, to a hoisting drum 32. The elevator car C and counterweight CW (see Fig. 8) are suspended, in a usual manner, by cables passing over the drum 32. A spring-pressed, electromagnetically-released brake 33, of a usual type. is mounted on the shaft of motor 30.

As shown in Fig. 7, windings of the motor 30 may be connected to a three-phase alternatingcurrent source 34, through conductors 34a, 34b and 340, by means of a starting device 35 and either one of a pair of reversing switches 36 and 37. A manual switch 38 is interposed between the alternating-current source 34 and the reversing switches 36 and 37.

A pair of supply conductors L1 and L2 are connected to the alternating-current conductors 34a, 34b and 34c, between the manual switch 38 and the reversing switches 36 and 37, by means of suitable rectiflers 39. The rectifiers 39 and be connected to supply conductors L1 and L2,

by means of a circuit including contact members 35:: of a starting device 35, contact members of starting switch 41, front contact members of either of the reversing switches 36 and 37 and front contact members of a brake relay 42.

The operating coil of starting device 35 is connected to supply conductors L1 and L2 by means of a circuit which includes front contact members of reversing switches 36 and 37, in parallel, and contact members of the brake relay 42.

The starting device 35 may be any usual form of time-element switch having contact members operable at time intervals suitable for the purposes of the invention. For simplicity, we have illustrated the starting device 35 as a dashpotcontrolled time-element switch provided with front contact members 35a, 35b, 35c, 35d, 35c, 35! and 35:: and with back contact members 351/ and 352. The timing of the contact members is as follows: upon energization of the operating coil of the device, front contact members 35c, 35d and 35;: close, and back contact members 35;; and 352 open, substantially instantaneously. Subsequently, after a time interval sutficient for the initial peak of the motor-starting current to fall, contact members 350 and 35 close. After a second time interval, sufficient for the second peak of motor starting to fall, the contact members 35b and 35a close. Upon deenergization of the operating coil of starting device 35, contact members 350 and 35d open substantially instantaneously, and, after a brief interval, contact members 35a, 35b, 35c, 35] and 35:: open. After an interval of time sufliclent to permit a. passenger or prospective passenger to open the car gate or a hatchway door, contact members 353 reclose. After a longer period, sufiicient to perrnit a prospective passenger to open a hatchway door and the car gate, enter the car, close the door and gate and register a call on a push button within the car, the contact members 352 roclose.

A power-responsive relay 43, of the type shown in Figs. 1 to 5, is provided for commutating variable portions of the resistor R3 in accordance with the power supplied to the primary windings of motor 30.

A door relay 40, controlled by contact members of brake relay 42, contact members 351/ of starting device 35 and contact members 411': of starting switch 41, is provided for controlling a circuit for the operating coil 44a of a direction-preference relay 44.

The function of the direction-preference relay 44 is to prevent reversal of the elevator car in response to calls registered at floors which the elevator car has passed, until all calls registered at floors in advance of the elevator car have been answered. In addition to the operating coil 44a, the relay 44 is provided with a demagnetizing coil 44b, controlled by back contact members of the starting switch 41 and contact members 352 of the starting device 35.

- A pair of interlocked relays 45 and 46 are provided for controlling the circuits of the operating coils of reversing switches 37 and 36, respectively. The interlock relays 45 and 46 and the starting switch 41 are controlled by a plurality of call relays 47, 48 and 49, operating in conjunction with a plurality of hatchway switches F1, F3 and F3, in a manner to be hereinafter more fully described.

The call relays 47, 48 and 49 serve to record the calls registered by passengers or prospective passengers until the calls are answered. Each of the call relays 47, 48 and 49 comprises an operating coil 47a, 48a and 49a, respectively, a demagconnected to supply conductor L1 by means of a common conductor 50, in series with back contact members of a by-pass relay 51. The by-pass relay 51 is preferably of a slow-acting type and is controlled by contact members of a power-responsive relay 52, similar to that shown in Figs 1 to 5, except that it is provided with two independently adjustable contact members 52d and The purpose of the by-pass relay 51 is to prevent the stopping of the elevator car C. in

response to operation of a hall push button, H1, H2 or H3, when the car is fully loaded. 1

The connections of relays 43 and 52, by which they respond to power flowing in the circuit of motor 30, may now be described. The current coils 43a and 52a of the relays 43 and 52 are connected in circuit with one conductor (340) in the circuit of the windings of motor 30. The voltage coils 43b and 52b and the armature coils 43c and 52c 01 the relays 43 and 52, respectively, are connected in any suitable manner to respond to a voltage proportional to the line voltage supplied to the motor 30, and in phase with the power component of the currentflowing in the conductor (34c) in which the current coils are connected. In the arrangement shown, a pair of resistors 431' and 521', having mid-taps, are connected between the conductors 34a and 34b. The armature coil 43c and the voltage coil 43b of relay 43 are connected in series between the conductor 34c and the mid-tap of resistor 431'. The armature coil 52c and the voltage coil 52!) of relay. 52 are connected in series between the conductor 34c and the mid-tap o! the resistor 52r.

The hatchway switches F1, F2 and F3 are ofidentical construction and are located one at each floor served by the elevator car. The construction of these switches may best be understood by reference to the switch F1 for the first floor (Fig. 8) to which reference characters have been applied. The hatchway switch F1 comprises two contact arms Fa and Fb, insulated from each other and rotatably mounted on suitable pivots. The contact arms Fa and Fb may be rotated about their pivots by means of a roller Fe so positioned as to cooperate with a cam mounted on the elevator car C. The movable parts of the switch are so biased, by any suitable means, (not shown) that the switch is stable in any of three operating positions, to each of which it may be moved by the cam G. The contact arm Fa is so mounted that it may engage any one of the three contact members Fd, Fe or Ff, depending upon the position of the arm. The contact arm Fb is mounted in such a manner that it may engage a contact member Fg when the contact arm Fb is in the'position shown in the figure, but may not engage any contact member when in either of its other operating positions. The cam G on the car cooperates with the hatchway switch F1 in such manner that, when the car is within a predetermined region adjacent to the first floor, represented by the central vertical portion of cam G, the contact arm Fa engages contact member Fe, and the contact arm Fb engages contact member Fg. When the car C is in any position above the predetermined region mentioned above, the contact arm Fb is disengaged and the contact arm'Fa engages the lower contact member Ff. When the car is in any position below the predetermined region, the

contact arm Fb is disengaged, and the contact arm Fa engages the upper contact member'Fd. The usual door contact members 53, 54 and 55 and gate contact members 56 are interposed in the circuit 0! door relay 40.

The operation of the above-described apparatus may be set forth as follows: preliminary to operation of the car C in response to the push buttons C1 to C3 and H1 to H3, the manual switch 38 is closed. After closure or the switch 38, operation of the car may be initiated in response to the push buttons. Assuming that a prospective pass senger at the third floor wishes to use the elevator, he presses the push button H3. Upon pressing the push button H3, a circuit for the operating coil 47a of call relay 4'7 is completed as follows: from supply conductor L1, through contact members of relay 51, conductor 50, push but-- ton H3 and the operating coil 47a, to supply conductor L2.

Upon completion of this circuit, the call relay .4! closes, to establish a holding circuit for itself, through its contact members 470, and to complete acircuit for the operating coil of interlock relay 45. The latter circuit may be traced from supply conductor L1, through the contact members 470 and 4711 01 the call relay 47, the lower contact arm oi. floor switch F3, back contact members 44c 01' direction-preference relay 44, back contactmembers of interlock relay 46 and the operating coil oi interlock. relay 45, to supply conductor L2. a

The relay 45 closes to complete a circuit for the operating coil of starting switch 41 by means of its contact members 45a; to open interlock contact members 45b in the circuit of the operating coil of interlock relay 46; to partially complete a holding circuit for itself through its contact members 450 and to partially complete a circuit for the operating coilv of reversing switch 37, through its contact members 45d. The circuit for the operating coil of starting switch 41 extends from supply conductor L1, through contact members 470 and 47d of call relay 4'7, the lower arm of floor switch F3, contact members 450, of relay 45 and the operating coil of switch 41 and resistor R4, to supply conductor L2.

The starting switch 41 now closes to complete a holding circuit for the interlock relay 45; to open contact members in the circuit of the de-' magnetizing coil 44b of relay 44; to complete a circuit for the operating coil of relay 42 by means of its contact members 410; to partially complete a circuit for the operating coil of reversing switch 37 and relay 43- by means of contact members 41b; to partially complete a circuit for the release coil of brake 33 and to partially open the local circuit connecting the resistor R3 with the release coil oi brake 33, by means of its contact members 41a. The circuit for the operating coil of relay 42 may be traced from supply conductor L2, through contact members 35y of starting device 35, contact members 41b and.4lc of switch 41 and the operating coil of relay 42, to supply conductor L1.

Upon completion of the circuit for relay 42, as traced above, relay 42 closes to complete a circuit for theoperating coil of door relay 40; to partially complete a holding circuit for the relay 40 and to partially complete a circuit for the operating coil oi the starting device and the release coil of brake 33. The circuit for the operating coil of door relay extends from supply conductor L2, through contact member 35 of the starting device 35, contact members 41b 01 the switch 41, gate contact members 56, door contact members 53, 54 and 55, contact members of relay 42, the operating coil of door relay 40, to supply-conductor L1.

The door relay 40 now closes to complete a circuit for the operating coil 44a of directionpreference relay 44; to complete a circuit for the reversing switch 37 and to complete a holding circuit for itself. The circuit for the operating coil 0! direction-preference relay 44 may be traced from supply conductor L2, through the operating coil 44a and contact members of relay 40, to supply conductor L1. The circuit for the operating coil of reversing switch 37 may be traced from supply conductor L2, through contact members 351 of starting device 35, contact members 41b of switch 41, contact members d of the interlock relay 45, the operating coil of reversing switch 3'1 and contact members of door relay 40, to supply conductor ,L1. The holding circuit torthe door relay 40 extends from supply conductor L2, through contact members oi relay 42, contact members of the door relay 40, gate contact members 56, door contact members 53, 54 and 55, contact members of brake relay 42 and the operating coil oi. doorrelay 40, to supply conductor L1.

Ascircuits have been completed for the direction-preference relay 44 and the reversing switch 37. the direction-preference relay 44 and reversing switch 37 now close. Relay 44, in closing, opens its contact members 44] in the closing circult of interlock relay 48; opens its contact members 442 in the closing circuit of interlock relay 45: closes its contact members 44c in the circuit of interlock relay 45 and completes a holdng circuit for itself through closure oi. its contact The interlock relay 45 remains closed, notwithstanding the opening of contact members 44c in its closing circu t, because 01 the independent circuit established by closure of switch 41, as described above. The holding circuit for relay 44 may be traced from supply conductor L1, through contact members 44d and the operating co'l 44a of relay 44, to supply conductor L2.

. The reversing switch 37, in closing, establishes a holding circuit for the starting switch 41; completes a circuit for the operating col of startin: device 35 and the release coil of brake 33; disconnects the resistor R3 from the terminals of the release coil of brake 33. and partially completes a circuit for the wind ngs or motor 30.

Upon'completion of the circuit for the operating coil of starting device 35, the starting device 35 commences to operate, immediately clos ng its contact members 35d, 35c and 35.1: and opening its contact members 351/ and 35:. The closure 0! contact members 350 and 35d establishes an energizing circuit for the windings of motor. 30 in series with the resstor sections R5 and R6. The opening or contact members 352 has no immediate efiect because the circuit of the demagnetizing coil 44b of relay 44 is, at this time, open at contact members of switch 41. The opening of contact members 351 has no immediate effect, as a circuit for the relay 43, the relay 42 and the reversing switch 37, has been independently established through contact members or re1ays.40

and 42. The closure of contact members 34;: completes a circuit for the release coil of brake 33. This circuit may be traced from supply conductor L2, through contact members 35: of start'ng device 35, contact members of switch 41, the release coil of brake 33, contact members of relay 42, contact members of reversing switch 37 and to supply conductor Ll.

The brake 33 is now released, and the elevator car moves upward, the starting current for the Ielevator motor 30 beinglimited by the resistor sections R5 and R6. At the expiration of a predetermined interval of t'me after the closure of contact members 35c and 35d, contact members 35b and 35c 01' the starting device 35 close, to short-circuit the resistor sections R5. After another predetermined time interval, contact members 35a and 35] close to short circuit the resistor sectons R6, thereby causing the motor 30 to accelerate to full speed. I

During the acceleration process described above, and thereafter, when the motor30 is operating at steady speed, the armatures of relays 43 and 52 rotate to positions corresponding to the power drawn by the motor 30 at each instant. If, during the acceleration power peak, the contact arm of relay 52 engages the contact member 52d, 8. circut for the operating coil of the by-pass relay 51 is momentarily completed. Re lay 51 does not close, however, because of its time relay, unless, because of a iully loaded car, the contact arm of relay 52 remains in engagement with a contact member 52d or 52c alter the motor has accelerated to steady speed.

The position of the armature of relay 43 determined the fractional portion of resistor R3 which is included in the discharge circuit of the release coil oi? brake 33. If the unbalanced load is such that the motor 30 draws power from the source 34, the contact arm 0! relay 43 rotates clockwise so that only a small proport=on of resistor R3 is included in the discharge circuit. If, on the other hand, the unbalanced load is overhauling so that the motor 30 is driven above -synchronous speed and returns power to the source 34, the contact arm of relay 43 rotates counter-clockwise to such postion that a large part of resistor R3 is included in the discharge circuit. This adjustment of the resistor R3 has no immediate effect, as the discharge crcuit of the operating coil of the brake 33 is now open but is a preparatory step for the deceleration process to be hereinafter more fully described.

11', while the car is moving upwardly and before it has reached the second floor, a prospective passenger at the second floor desires to use the car, he presses the hall button H2. This completes a circuit for the operating coil of call relay 48 which may be traced as follows: from supply conductor L1, contact members of by-pass relay 51, through the push. button H2, thence, through the operating coil 48a of call relay 48, to supply conductor L2. The call relay 48.now closes to establish a holding circuit for itself through its contact members 48c and 48d. The closure of call relay 48 has no immediate effect on the interlock relay 45 because the latter is already closed.

The elevator car C continues to move upwardly until the car is a proper slow-down distance in advance of the second floor, when the roller of the hatchway switch F2 engages the central vertical portion of the cam G on the elevator car. When this occurs, the hatchway switch F2 moves into a horizontal position, to establish a circuit for the demagnetizing coil 48!) of call relay 48, through its upper arm Fb, to complete a short circuit around the operating coil of switch 41 by means of its lower arm Fe. The circuit for the demagnetizing coil 48b of call relay 48 extends from supply conductorLl, through contact members 48c and the demagnetizing coil 48b of relay 48, thence, through the upper arm Fb of hatchway switch F2, to supply conductor L2. The short circuit for the operating coil of switch 41 extends from supply conductor L1, through contact members 48c and 48d of the call relay.48, the lower arm Fa of floor switch F2 and the central contact member Fe associated therewith, thence, through resistor R4, to supply conductor L2. The resistor R4 limits the short-circuit current to a low value.

The call relay 48 and the starting switch 41 now drop out. The starting switch 41, in dropping out, opens its contact members in the holding circuit of interlock relay 45; partially completes a circuit for the demagnetizing coil 44!; of the direction-preference relay 44; opens the circuit of the brake relay 42 at its contact members 41c; opens the circuit of door relay 40 and the circuit of reversing switch 37 at its contact members 41b; establishes a discharge circuit for the release coil of brake 33 by closure of its contact members 41a and immediately thereafter disconnects the release coil of brake 33 from the supply conductors L1 and L2.

In response to the opening of starting switch 41, the reversing switch 37, the door relay 40 and the brake relay 42 drop out. The interlock relay 45 and the direction-preference relay 44 remain closed, however, as the contact members 35a of starting device 35 are. at this time, open.

The reversing switch 37, in dropping out, breaks the holding circuit of starting switch 41; breaks the circuit of the operating coil of starting device 35; disconnects the motor 30 and completes a circuit in parallel to the contact members 41a of starting switch 41.

The door relay 40, in'dropping out, opens contact members in the circuit of direction-preference relay 44, opens contact members in the circuit of reversing switch 37 and opens its holding circuit.

The brake relay 42, in dropping out, opens contact members in the closing circuit oi door relay 40; opens contact members in the common circuit of the operating coil of starting device 35 and the release coil of brake 33 and opens contact members in the holding circuit of door relay 40.

As the circuit for the operating coil of starting device 35 is now open, the starting device 35 commences to operate to open position, immediately opening its contact members 350 and 35d, and, after a brief interval, opening its contact members 35a, 35b, 35e, 35) and 35:0. The back contact members 35 and 352 do not immediately close, however, but remain open for several seconds, as previously explained.

It will be recalled that, upon movement of the hatchway switch F2 to a horizontal position, a circuit for the demagnetizing coil 48b of call relay 48 was completed through the upper arms Fb of hatchway switch F2. In response to completion of this circuit, the call relay 48 drops out. The call relay 48, in dropping out, breaks the short circuit around the operating coil of starting switch 41. As, upon interruption of this short circuit, the closing circuit for starting switch 41,

own

originally established by closure of the call relay 47 for the third floor, again becomes effective, and the Starting switch 41 immediately recloses.

The reversing switches 36 and 37, the door relay 40 and the brake relay 42 are now open; the interlock relay 46, the direction-preference relay 44 and the starting switch 41 are closed; the closing circuit of starting device 35 is broken, but the delayed contact members 35g and 35a have not yet reclosed.

The release coil of brake 33 is now disconnected from the supply conductors L1 and L2 and connected in a local circuit with a portion of resistor R3, determined by the position of the armature of power-responsive relay 43, as previously explained. A transient current now circulates in the local circuit, while the resistance of the circuit absorbs the energy stored in the highly inductive release coil. As the transient current decreases, the brake shoe is gradually applied by the brake spring, bringing the car smoothly to rest. If ,at.

the instant before the motor 30 is disconnected, the unbalanced load is such that the motor returns power to the source 34, a relatively large part of resistor R3 is included in the local circuit, and the transient is highly damped, so that the brake sets rapidly. However, if, at the instant before being disconnected, the motor 30 draws power from the source 34, a relatively small part of resistor R3 is included in the local circuit and the transient persists for a longer time interval to cause the application of the brake to be retarded. As previously explained, the adjustment of the v resistor R3 in accordance with the unbalanced load, approximately compensates for all variables affecting the slow-downdistance, so that the car stops level with the floor, regardless of load conditions;

The elevatorcar C now stands level with the second floor, a call has been registered for'the third floor but the contact members 351 and 352 of starting device 35 have not yet reclosed. If, within the period of several seconds before the contact members 35y reclose, the prospective passenger at the second floor opens the hatchway door, the door contact members 55 are opened to prevent the closure of door relay 40 and hence the starting of the car until all doors and gates are closed. If, however, the prospective passenger fails to open the hatchway door before the contact members 35y reclose, the car will start upward in response to the registered call for the third floor, when the contact members 35y reclose. The car may thus start upward in response to closure of all doors and the car gate, if any of them has been opened, or in response to the closure of contact members 35y, if no door or gate has been opened.

Assuming that the prospective passenger has opened the hatchway door and the car gate, at the second floor, and entered the car and closed the hatchway door and car gate, the operation is as follows: as soon as the contact members 35y of the starting device 35 reclose, a circuit for the brake relay 42 is completed. This circuit may be traced from supply conductor L2, through contact members 35y of starting device 35, contact members 41b and 410 of starting switch 41 and the operating coil of brake relay 42, to supply conto complete "up" connections for the motor 30 and to energize the operating coil of starting device 35, in the manner explained in connection with the starting of the car from the first floor. Starting device 35 now operates to closed position, in the manner previouslyexplained, immediately closing its contact members 35c, 35d and 35a: and opening its contact members 3511 and 352. The closure of contact members 35b and 35c and, subsequentlyz'the closure of contact members 35a and 35] follow, bringing the motor 30 up to full speed. The car now continues upward until the roller of hatchway' switch F3 is engaged by the central vertical portion of the cam G on the car. When this occurs. the hatchway switch F3 moves to a horizontal position to bring the car C to rest at the third floor, in the manner described in connection with the stopping operation at the second floor.

It will be noted that, in the system described above, one of the interlockrelays 45 or 46 closes in response to the first push button pressed and, if more than one call for the same direction is registered, remains closed while the elevator car is stopped at any intermediate floors in advance of the floor from which the terminal call was registered. During the time the interlock relay 45 is closed, it prevents closure of the interlock relay 46, in this way preventing the elevator car from responding to calls in the opposite direction until all calls in the direction of travel of the car have been answered. Similarly, it interlock relay 46 is closed, it prevents closure of interlock relay 45. After the last call for one direction of travel has been answered, and the elevator car has remained at the floor for a predetermined period of time, contact members 352 of the starting device 35 close to complete a circuit for the demagnetizing coil 44!) of relay 44. This circuit extends irom supply conductor L1, through contact members 44d and the demagnetizing coil 44b of relay 44, contact members of switch 41 and contact members 352 of starting device 35, to supply conductor L2. Upon completion oi! this circuit, the relay 44 drops out. Relay 44. in dropping out, breaks the circuit of interlock relay 45 at its contact members 44c. Both interlock relays 45 and 46 are now open, and the elevator car may be calledtoanyotherfloorinresponsetotheoperation of a push-button switch.

If, at any time during the operation of the elevator car, the elevator operates so that the motoring load on the elevator motor exceeds a value determined by the adjustment of the adjustable contact member 52d of the relay 52, a circuit is completed for the operating coil of the by-pass relay 51. If, on the other hand, the elevator motor operates with an overhauling load that exceeds a value determined'by the adjustment of adjustable contact member 52c of relay 52, a similar circuit is completed for the operating coil of relay 51. If either of these load conditions persists for a period of time exceeding the acceleration period of the motor 30, the by-pass relay 51 operates to break the common circuit 50 for the hall push buttons. This arrangement permits the car to pass floors at which prospective passengers have registered calls when the car is fully loaded, but does not prevent the stopping of the car in response to operation of the car push buttons C1 to C3.

It will be understood that the above described elevator system is illustrative only and that many devices which would be used in practice have been omitted for simplicity.

We do not wish to be restricted to the specific structural details, arrangement of parts or circuit connections herein set forth, as various modifications thereof may be effected'without departing from the spirit and scope of ourinvention. We desire. therefore that only such limitations shall be imposed as are indicated in the appended claims.

We claim as our invention:

1. In a motor-control system, a motor, an automatically applied brake for said motor, said brake having a release coil, a source of current for said release coil, means for energizing and deenergizing said motor, means responsive to an electrical characteristic of said motor which varies with the load, including relatively movable elements for recording the load on said motor when it is operating at steady speed, and means controlled by said relatively movable elements for controlling the current in said release coil, after said motoris deenergized, to bring said motor to rest with a uniform amount of rotation after deenergization, regardless of motor load.

2. In a motor-control system, a motor; an automatically applied brake for said motor, said brake having a release coil, a source of current for said release coil, means for energizing and deenergizing said motor, means responsive to an electrical characteristic of said motor whichvaries with the load, including relatively movable elements for recording the load on said motor when said motor is operating at steady speed, control means for initiating a stopping operation of said motor, and means, controlled by said relatively movable elements for controlling the current in said release coil after operation of said control means, to bring said motor to rest with a uniform amount of rotation after initiation of a stepping opera tion, regardless of motor load.

3. In a motor-control system, a motor, an automatically applied brake for said motor, said brake having a release coil, a source of current for said release coil, means for energizing and deenergizing said motor, means responsive to an electrical characteristic of said motor which varies with the load, including relatively movable elements for recording the load on said motor when said motor is operating at steady speed, a discharge circuit for said release coil, and means controlled by said relatively movable elements for controlling the resistance of said discharge circuit, after said motor is deenergized, to bring said motor to rest with a uniform amount of rotation after deenergization, regardless of motor load.

4. In a motor-control sysem, a motor, an automatically applied brake for said motor, said brake having a release coil, a source of current for said release coil, means for energizing and deenergizing said motor, means responsive to an electrical characteristic of said motor which varies with the load including relatively movable elements for recording the load on said motor when said motor is operating at steady speed, 11 discharge circuit for said release coil, control means for initiating a stopping operation of said motor, and means controlled by said relatively movable elements for controlling the resistance of said discharge circuit, after operation of said control means, to bring said motor to rest with a uniform amount of rotation after initiation of a stopping operation, regardless of motor load.

5. In a motor-control system, a, motor, a motor circuit therefor, an automatically applied brake for said motor, said brake having a release coil,

an energizing circuit and a discharge circuit for said release coil, means responsive to an electrical characteristic of said motor which varies with the load, including relatively movable elements for recording the load on said motor when said motor is operating at steady speed, means controlled by said relatively movable elements for controlling the resistance of said discharge circuit, means for completing said motor circuit and said energizing circuit to start said motor and means for breaking said motor circuit and said energizing circuit and completing said discharge circuit; whereby said motor is brought to rest with a uniform amount of rotation after disconnection, regardless of motor load.

6. In an elevator-control system, an elevator car, a counterweight, a motor for driving said car and counterweight, means for energizing, deenergizing and reversing said motor, means responsive to an electrical characteristic of said motor which varies with the unbalanced load including relatively movable elements for recording the unbalanced load on said motor when said motor is operating at steady speed, and means controlled by said relatively movable elements for controlling the deceleration of said car to bring said car to rest in a uniform slow-down distance, regardless of load.

7. In an elevator-control system, an elevator car operable in a hatchway, a counterweight, a motor for driving said car and said counterweight, means for energizing, deenergizing and reversing said motor, means responsive to an electrical characteristic of said motor which varies with the unbalanced load, including relatively movable elements for recording the unbalanced load on said motor when said car is at a predetermined point in said hatchway, and means controlled by said relatively movable elements for controlling the deceleration of said car to bring said car to rest in a uniform slow-down distance, regardless of load.

8. In an elevator-control system, an elevator car operable in a hatchway past a landing, a counterweight, means for energizing, deenergiz ing and reversing said motor, means responsive to an electrical characteristic of said motor which varies with the unbalanced load, including relatively movable elements for recording the unbal- 1 anced load on said motor when said motor is operating at steady speed, slow-down means, responsive to the position of said car, for initiating a deceleration operation of said car at a predetermined point in advance of said landing, and means controlled by said relatively movable elements for controlling the deceleration of said can after operation of slow-down means, to bring said car to rest at said landing, regardless of load.

9. In an elevator-control system, an elevator car, a counterweight, a motor for driving said car and said counterweight, an automatically applied brake for said motor, said brake having a release coil, a source of current for said release coil, nieans for energizing, deenergizing and reversing said motor, means responsive to an electrical characteristic of said motor, which varies with the unbalanced load including relatively movable elements for recording the unbalanced load on said motor when said motor is operating at steady speed, and means controlled by said relatively movable elements for controlling the current in said release coil, during a deceleration operation, to bring said car to rest in a uniform slow-down distance, regardless of load.

10. In an elevator-control system, an elevator car operable in a hatchway, motor for driving said car and said counter- Weight, an automatically applied brake for said motor, said brake having a release coil, a source of current for said release coil, means for energizing, deenergizing and reversing said motor, means responsive to an electrical characteristic oi said motor which varies with the load, including relatively movable elements for recording the unbalanced load on said motor when said car is at a predetermined point in said hatchway, and means controlled by said relatively movable elements for controlling the current in said release coil during a deceleration operation, to bring said car to rest in a uniform slow-down distance, regardless of load.

11. In an elevator-control system, an elevator car operable in a hatchway past a landing, a counterweight, a motor for driving said car and counterweight, an automatically applied brake for said motor, said brake having a release coil, a source of current for said release coil, means for energizing, deenergizing and reversing said motor, means responsive to an electrical characteristic of said motor which varies with the unbalanced load, including relatively movable elements for recording the unbalanced load on said motor a counterweight, a

when said motor is operating at steady speed,

slow-down means, responsive to the position of said car, for initiating a deceleration operation oi said car at a predetermined point in advance of said landing, and means controlled by said rela tively movable elements for controlling the current in said release coil, after operation of said I slow-down means, to bring said car to rest at said landing, regardless of motor load.

12. In an elevator-control system, an elevator car operable in a hatchway past a landing, a counterweight, a motor for driving said car and said counterweight, an automatically applied brake for said motor, said brake having a release coil, means for energizing, de-energiaing and reversing said motor, means responsive to an electrical characteristic of said motor which varies with the unbalanced load, including relatively movable elements for recording the unbalanced load on said motor when said motor is operating at steady speed, slow-down means, responsive to the position of said car for initiating a deceleration operation of said car at a predetermined point in advance of said landing, a discharge circuit for said release coil, and means controlled by said relatively movable elements for controlling the resistance of said discharge circuit, after operation of said slow-down means, to bring said car to rest at said landing, regardless ,of load. l

13. In an elevator-control system, an elevator car operable in a hatchway past a landing, a counterweight, a motor for driving said car and counterweight, a motor circuit for said motor, an automatically applied brake for said motor, said brake having a release coil, an energizing circuit and a discharge circuit for said release coil, means responsive to an electrical characteristic of said motor which varies with the unbalanced load on said motor, including relatively movable elements for recording the unbalanced load on said motor when said motor is operating at steady speed, slow-down means, responsive to the position of said car, for initiating a deceleration operation of said car at a predetermined point in advance of motor circuit and said energizing circuit and completing said discharge circuit to bring said car to rest at said landing, regardless of load.

KENNETH M. WHITE. LUTHER. J. KINNARD. 

